The invention relates to a device for picking up a sheet trailing edge from an upstream cylinder, as viewed in sheet travel direction, and for transferring the sheet to a gripper system, especially in a sheet-fed rotary printing press.
A device of this general type has been disclosed heretofore in German Published, Non-Prosecuted Patent Application DE 198 33 903 A1, corresponding to U.S. Pat. No. 6,401,610. The functional principle of such so-called single-drum turning or reversing, requires storage on the upstream impression cylinder of the sheet to be turned or reversed. Gripping and removal of the trailing edge therefore has to be performed by suckers, which transfer the trailing edge to grippers of the turning drum before the leading edge is released by the grippers of the impression cylinder. In order to have the largest possible machine angle intervals available for these transfer operations and to peel off the trailing sheet region from the impression cylinder with as continuous a tangent as possible and to be able to transfer the trailing sheet region to further gripper elements of the turning drum, the application of suction to the trailing edge must begin as early as possible. The suckers, which are located on a sucker carrier, have to move along a curved path which contains three sections required by the process. In addition, in all three sections, specific positional angles of the suction surfaces to the impression cylinder are required, for the trailing sheet region to be peeled off and for the pad of the turning drum gripper to which the sheet trailing edge is transferred.
In order to implement or realize the here in a forementioned movement sections, which have to be executed within a cylinder rotation angle of about 25xc2x0, a dynamically stable guide mechanism is necessary. A precondition therefor is that the mass of the elements of the mechanism be inversely proportional to the size of the movement executed thereby.
Because the sucker carrier sweeps over extreme paths and rotational angles, and is therefore subjected to extreme acceleration, mass and mass moment of inertia have to be kept as low as possible. On the other hand, adequate stiffness of this component is required, in order for it to possess the necessary stability for the sheet transport and to be insensitive or indifferent to accidents (for example, sheets being pulled in and crumpled). The heretofore-known sucker guide mechanism according to German Published, Non-Prosecuted Patent Application DE 198 33 903 A1, corresponding to U.S. Pat. No. 6,401,610, does not optimally meet the aforementioned requirements.
It is an object of the invention to provide a device for picking up a sheet trailing edge from an upstream cylinder and for transferring the sheet to a gripper system, the device having a low-mass sucker carrier which has, nevertheless, good stiffness characteristics, comparable with those of corresponding steel construction.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for picking up a sheet trailing edge from an upstream cylinder and transferring the sheet trailing edge to a gripper system of a downstream drum, as viewed in sheet travel direction. The device comprises a sucker guide mechanism having a movably mounted sucker carrier whereon sucker heads subjectible to an application of vacuum or suction air are disposed. The sucker carrier is constructed as a tubular part having a longitudinal axis and being movable perpendicularly to the longitudinal axis thereof. The tubular part is formed with a vacuum or suction air duct extending in the interior thereof and being formed of carbon fiber-reinforced plastic-material laminate.
In accordance with another feature of the invention, the gripper system is an assembly of turning or reversing grippers.
In accordance with a further feature of the invention, the sucker heads, respectively, are connected mechanically and pneumatically to the tubular sucker carrier via sucker tubes disposed at intervals in a row on the sucker carrier, transversely to the longitudinal axis of the sucker carrier.
In accordance with an added feature of the invention, the sucker tubes are also formed of carbon fiber-reinforced plastic-material laminate.
In accordance with an additional feature of the invention, the pick-up device further comprises a suction air or vacuum connecting piece disposed on the tubular sucker carrier, for supplying suction air or vacuum.
In accordance with yet another feature of the invention, the sucker carrier and sucker tubes are lined on the inside thereof with a foam cambric for reducing suction-air flow cross section.
In accordance with yet a further feature of the invention, the cross-sectional area of the suction-air duct in the tubular sucker carrier is 10% to 30% of the internal cross section prescribed by the carbon fiber-reinforced plastic-material covering.
In accordance with yet an added feature of the invention, the suction-air flow cross section within the sucker tubes, respectively, is 20% to 40% of the sucker tube cross section overall.
In accordance with yet an additional feature of the invention, the foam cambric is formed of a low-mass thermoplastic material.
In accordance with still another feature of the invention, the foam cambric is rigid and is formed of a reactive, closed-cell polyurethane foam.
In accordance with still a further feature of the invention, the low-mass thermoplastic material has a bulk density of about 50 g/dm3.
In accordance with still an added feature of the invention, the rigid foam cambric has an integral structure wherein both in the inner layer thereof adjacent to the suction air duct and in the outer layer thereof adjacent to the carbon fiber material, it has a high density of about 800 g/dm3 and, in the interior lying therebetween, has a lightweight foam structure of about 20 g/dm3.
In accordance with still an additional feature of the invention, the pick-up device further comprises articulated levers engaging with the tubular sucker carrier, the levers and the vacuum or suction-air connecting piece being formed of carbon fiber-reinforced plastic-material laminate.
In accordance with another feature of the invention, the sucker carrier, the sucker tubes, the articulated levers and the suction air or vacuum connecting piece are connected to one another form-lockingly and by locking or joining of material.
In accordance with a further feature of the invention, the articulated levers and the suction air or vacuum connecting piece are also formed of carbon fiber-reinforced plastic-material laminate and a polyurethane core.
In accordance with an added feature of the invention, the carbon fiber-reinforced plastic-material covering of the tubular sucker carrier is formed of a plurality of layers of carbon fiber fabric, which have a given fiber orientation for high flexural and torsional rigidity.
In accordance with an additional feature of the invention, the tubular sucker carrier has a +45xc2x0/xe2x88x9245xc2x0 fiber orientation, with respect to the longitudinal axis thereof, over about 50% of the wall thickness of the carbon fiber structure thereof.
In accordance with yet another feature of the invention, the tubular sucker carrier is provided with a 0xc2x0 fiber orientation uniformly in the direction of the longitudinal axis thereof over about 50% of the wall thickness of the carbon fiber structure thereof.
In accordance with yet a further feature of the invention, the carbon fiber structure of the sucker tubes has a 0xc2x0 fiber orientation extending uniformly in the direction of the longitudinal axis of the respective sucker tubes.
In accordance with yet an added feature of the invention, the pick-up device further comprises carbon fiber plastic-material rings formed by circumferential windings disposed at free ends of the sucker tubes, the rings serving for reinforcing the sucker heads and for increasing resistance with respect to a transverse force introduced via the sucker heads.
In accordance with a concomitant feature of the invention, the tubular sucker carrier is constructed as one of binary and tertiary mechanism elements and, accordingly, has a group selected from two and three integrated articulated elements, respectively, of the sucker guide mechanism, a plurality of which is to be disposed over the width of the sucker carrier.
Thus, the sucker carrier according to the invention, including the elements connected mechanically and pneumatically thereto, constitutes a low-mass component nevertheless having a high stiffness. The loading of the elements of the mechanism and the joints of the sucker guide mechanism is thereby reduced considerably, which advantageously leads to a reduction in the deformations caused by inertia. Simultaneously, the inherent or characteristic frequency of the mechanism is increased, as a result of which undesired resonances are displaced to higher drive angular speeds. Both effects increase the operating accuracy of the mechanism and the maximum possible operating rotational speed.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for picking up a sheet trailing edge from an upstream cylinder and transferring the sheet trailing edge to a gripper system, especially in sheet-fed rotary printing presses, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
FIG. 1 is a fragmentary diagrammatic and schematic view of a cylinder configuration in a sheet-fed rotary printing press with turning drum grippers and a sucker guide mechanism, shown in part;
FIG. 2 is a fragmentary perspective view of FIG. 1, showing the sucker guide mechanism in greater detail; and
FIG. 3 is a fragmentary enlarged cross-sectional view of FIG. 2 taken along the line III-III in the direction of the arrows.